A mobile radio communication device such as a user equipment (UE) should continuously monitor and update a known set of nearby mobile radio cells in order to maintain a robust communication link with a provider network. Accordingly, conventional UEs periodically measure and evaluate signals received from neighboring mobile radio cells in order to update the set of nearby radio cells. In a Long Term Evolution (LTE) system, this mobile radio cell search and detection process is typically based on an analysis of synchronization sequences such as primary synchronization signals (PSSs) and secondary synchronization sequences (SSSs) that are broadcast by each mobile radio cell. In addition to evaluating synchronization sequences contained in received signals, UEs may also calculate the reference signal receive power (RSRP) and reference signal received quality (RSRQ) of signals received from nearby mobile radio cells.
A UE typically maintains a current list of nearby mobile radio cells and associated mobile radio channel characteristics by periodically updating a stored set of mobile radio cell characteristics based on an evaluation of received mobile radio signals. This list of nearby mobile radio cells is conventionally used for a variety of purposes, such as reporting measurement results to the mobile radio communication network in order to support effective mobility management.
Two different methods are conventionally used for such a mobile radio cell search and measurement process. The first method dedicates a relatively large period of time to analyze each nearby detected mobile radio cell. For example, a UE implementing the first method may spend about 60 ms to 70 ms dedicated to receiving data from a single mobile radio cell. A UE will utilize a number of consecutively received signals, such as by averaging several successive synchronization sequences, to generate a single detection mobile radio cell search result. This method potentially provides a strong detection rate due to the large period of time dedicated to analyzing a single mobile radio cell. However, this method requires committing a significant amount of resources and time to obtain a single mobile radio cell search result, thereby resulting in drawbacks in memory consumption and power efficiency.
In contrast to the first method, the second conventional method devotes a relatively small time window to receive signals from a given mobile radio cell. Instead of analyzing a lengthy, continuous stream of data from a given mobile radio cell, the second method instead relies on short bursts, e.g. one or two half frames of data, to detect whether a signal is being broadcast from a given mobile radio cell. The second method makes a determination whether the mobile radio cell is present or not and quickly cycles to a new mobile radio cell. By repeating this process, the second method cycles through a set of potential candidate mobile radio cells and continuously updates the number of detection occurrences of each mobile radio cell, i.e. how many times each mobile radio cell is detected. A mobile radio cell that is detected multiple times is determined to be a valid nearby mobile radio cell, while those detected once or less are ignored.
The second method offers several advantages over the first method such as greater scheduling flexibility and power efficiency as well as reduced power consumption. Despite only utilizing short reception windows, the second method can achieve both a comparable detection rate and false alarm rate to the RSRP/RSRQ-based first method. However, the average new mobile radio cell detection time is always longer than the time interval of two adjacent mobile radio cell search events as a new mobile radio cell must be measured at least twice in order to yield a valid nearby mobile radio cell result. Therefore, the time spent on mobile radio cell search and measurement may disadvantageously long.